The present invention relates in general to the field of transportable containers for a great variety of materials including solid and liquid waste products. The invention finds particular, but not exclusive, utility in containers of the type adapted to be picked up and set off by a transport vehicle such as a truck or trailer with a suitable power lift device known as a "roll-off hoist".
Containers for freight, bulk materials, and other products come in numerous sizes and load capacities. It has been a common practice heretofore to pull each container, regardless of its size and loading, aboard the transport vehicle with its forward end abutting a fixed stop on the vehicle. With such a system, the center of gravity of the container may often be located in an unfavorable position on the transport vehicle, imposing unnecessarily high loading upon a weaker area of the vehicle frame and imparting unnecessarily heavy loading to the power lift of the hoist during a roll-off operation.
Generally, waste handling efficiency can be improved by increasing the size of the waste container. The size of the container is generally limited, however by the ability of the transporting vehicle to load, transport and unload the particular container. As described herein, one manner of container handling involves pivoting a hoist frame at its rearward end to an inclined loading position. A container is next pulled onto the hoist frame until the container releasably engages with a stop carriage. The hoist frame and container are then pivoted back to a horizontal position for transport. The stop carriage and the container are next slidably moved forwardly of the hoist frame to most favorably position the container on the vehicle trailer.
While such vehicles or trailers may be made long enough to accommodate very large containers, the correspondingly larger hoist frame, when pivoted to the inclined loading position, would extend correspondingly farther up into the air. As a container is pulled up the inclined hoist frame, the center of gravity is elevated to such a height that the vehicle approaches a very unstable and dangerous condition.
Increasing the length of the container hoist to accommodate very large containers also creates undesirable stress problems which are typically solved by using larger, heavier, more complicated and/or costlier materials and frame designs.
What is needed is a hoist which will load, transport, and unload small as well as very large containers without jeopardizing the stability of the hoist and without subjecting the hoist to excessive bending movements and stresses.